AE-19
Sources of gamma radiation
in a reactor core
Matts Roas
AKTIEBOLAGET ATOMENERGI
STOCKHOLM • S\\ HDJtN • 1959
AE-19
ERRATUM
The spectrum in Fig. 3 has erroneously been normalized
to 7. 4 MeV/capture. The correct spectrum can be found by multiplying the ordinate by 0. 64.
AE-19
Sources of gamma radiation in a reactor core
Matts Roos
Summary: In a thermal reactor the gamma ray sources of importance for
shielding calculations and related aspects are 1) fission, 2) decay of
fission products, 3) capture processes in fuel, poison and other
materials, 4) inelastic scattering in the fuel and 5) decay of capture
products. The energy release and the gamma ray spectra of these
sources have been compiled or estimated from the latest information
available, and the results are presented in a general way to permit
235
application to any thermal reactor, fueled with a mixture of U
and
238
U
• As an example the total spectrum and the spectrum of radiation
escaping from a fuel rod in the Swedish R3-reactor are presented.
Completion of manuscript April 1959
Printed Maj 1959
LIST OF CONTENTS
Page
Introduction
...........
1
1.
Prompt fis sion gamma rays
i
2.
Fission product gamma rays
2
3.
Uranium capture gamma rays
4
O -2 Q
4.
U
inelastic scattering gamma rays
5.
Gamma rays from capture in poison, construction
materials and moderator . . . . . * • » . . • . . . . . . . .
5
8
6.
Gamma rays from disintegration of capture products. .
8
7.
Total gamma spectra. Application to the Swedish
R3 -reactor
9
SOURCES OF GAMMA RADIATION IN A REACTOR CORE.
INTRODUCTION
In reactor shielding studies and related aspects it is of
importance to know the energy released as gamma radiation and
its spectral distribution. So far detailed calculations of the total
spectrum of gamma radiation from a reactor core have been
hampered by a very limited knowledge of the sources. However,
the large volume of relevant information published during 1958,
especially concerning the main sources, now facilitates an estimate based on fewer guesses than before.
The gamma ray spectra of different sources can most conveniently be compared when expressed in units of energy release
per fission per energy interval^ or MeV/f. MeV, and the integrated
spectra thus in MeV/f. However, only the spectra of prompt fission
and fission product radiations can without loss of generality be expressed in these units, whereas in capture processes, for instance,
the number of captures cannot be related to the number of fissions
without reference to a specific reactor. In order to show the relative importance of the different sources, we therefore in the last
section apply the general results to a particular reactor, the
Swedish R3 (MARGEN & al. 1958), for which we give the total
spectrum and the spectrum of radiation escaping from a fuel rod.
1.
PROMPT FISSION GAMMA RAYS
The spectrum of y-rays emitted within 5» 10
s of fission
has been measured in the energy ranges from 0.3 MeV to about
7.3 MeV by MAIENSCHEIN & aL(i958), from 0.015 MeV to
0.800 MeV by VOITOVETSKII & aL(l957) and from about 0.020
MeV to about 0.260 MeV by SKLIAREVSKII & aL (1957). It seems
possible to join the spectra of MAIENSCHEIN and SKLIAREVSKII
in the region between 0.26 MeV and 0.30 MeV, whereas the
spectrum of VOITOVETSKII matches the spectrum of SKLIAREVSKII
only at the softest gamma line (0. 03 MeV)s falling a factor 5 below
at 0.20 MeV and a factor 10 lower than MAIENSCHEIN ' s spectrum
in the region from 0. 30 MeV to 0. 60 MeV.
_ Q
The energy r e l e a s e d within 5*10 s of fission and within the
energy range 0 . 3 - 10 MeV (extrapolated from 7 , 3 MeV to 10 MeV)
is r e p o r t e d by MAIENSCHEIN to be 7 . 2 ± 0. 8 MeV/f, and within the
r a n g e 0. 015 - 0.260 MeV by SKLIAREVSKII to be about 0.24 ± 0. 05
MeV/f. In addition MAIENSCHEIN h a s found delayed gamma r a y s in
Q
the region between 5*10
range 0 . 1 - 2 MeV. The
the prompt radiation, or
released within 10 s is
7.9 MeV/f
L
s and 10 s after fission8 and in the energy
intensity is reported to be (5. 7 ± 0. 3) % of
about 0, 4 MeV/f. Thus the total energy
about
(1.1)
The spectrum shown in Fig.l is obtained by joining the spectra
of MAIENSCHEIN and SKLIAREVSKII, and is, to account for the
unknown spectrum of delayed gamma raysj normalized to 7.9 MeV/f.
2.
FISSION PRODUCT GAMMA RAYS
Several reports ( BLOMEKE and TODD 1957, KNABE and
PUTNAM 1958, MAIENSCHEIN & al. 1958, MILLER 1957, PERKINS
and KING 1958, PRAWITZ & al. 1958, SCOLES 1958 a,b, STEHN and
CLANCY 195 8 ) have recently been published on the gamma-radiation
of products of thermal fission of U
at various cooling times after
irradiation times of various durations. The reports of BLOMEKE
and TODD, MILLER, SCOLES, PRAWITZ & al. , and PERKINS
and KING are based on available chemical data and thus do not extend to very short cooling times. As the most short-lived isotopes
emit comparatively hard v-radiationj it is recognized that the extrapolation of decay curves down to zero cooling time might give results
which are too small by a factor of 4. It could be possible, however,
to obtain better agreement by taking into account new nuclear data
on very short-lived isotopes^ as reported for instance by O'KELLEY
& al. (1958).
MAIENSCHEIN 8t al. have measured the Y~ ra y spectra at
various cooling times down to about 1 second after irradiation for
time intervals sufficiently short to be considered instantaneous.
These values appear to give the best starting point at present in
an effort to evaluate the spectrum at zero cooling time and infinite
irradiation time. (There is essentially no change in the spectrum
between an irradiation time of a few hundred days and infinity,
for most reactors.) The total energy above 0.3 MeV emitted beQ
tween 1 s and 10 s after fission is reported to be 5.9 i 0.7 MeV/f
(MAIENSCHEIN has used the chemical data of PERKINS and KING
3
8
for extrapolation from 1.8» 10 s to 1 0 s). Extrapolating in
MAIENSCHEIN ' s curve from 1 s down to zero, one obtains an
increment of about 0.3 MeV/f. An estimate of the contribution from
energies < 0. 3 MeV can be based on the lowest energy group of
PERKINS and KING which extends down to 0.1 MeV. This gives
an additional increment of about 0. 3 MeV/fa bringing the total
energy release up to 6. 5 +. 0.7 MeV/f.
STEHN and CLANCY have made an extensive survey over
several measurements on (3- and v-activities at very short cooling
times (this survey includes some of the results reported by
MAIENSCHEIN)8 and they conclude that a reasonable value for the
total v -energy released would be about 7.0 MeV/f.
From the standpoint of shielding this value is slightly more
conservative than the value of MAIENSCHEIN. It thus seems reasonable to adopt it at present.
The fission product v-ray spectrum at zero cooling time and
infinite irradiation timej Fig. 2, has been constructed in the following way:
The energy release in each of the 6 energy groups is obtained
by extrapolating the photon-intensity time distributions of MAIENSCHEIN from 1 s to zero, integrating from zero to 1800 s, adding
a contribution for the time between 1800 s and 5* 10
s (it was
necessary to calculate this separately from the data of BLOMEKE
and TODD, for each isotope present and each gamma line, because
the similar calculations published by PERKINS and KING have an
energy grouping different from MAIENSCHEIN and are thus difficult
1) KNABE and PUTNAM give 6. 6 MeV/f for photons of energy > 0. 1
MeV released between Is and 10^ s.
to compare), multiplying by the group width and by the average
energy of the group. The average energy was estimated from the
continuous belt measurements of MAIENSCHEIN. The sum of the
6 groups, covering the energy range 0.3 - 5.0 MeV is found to be
6.5 MeV/f. This figure can be compared with the figure 5.9 i 0.7
MeV/f of MAIENSCHEIN plus the estimated contribution of energy
released within i s of fission, 0.3 MeV/f. The difference
6.5-5.9
0.3 = 0.3 MeV/f is probably attributable to the fact that the photon
intensity time-distributions are uncorrected for the spectrometer
response function, whereas the total energy release curve has an
approximate correction.
To the histogram of the 6 energy groups we finally add the
estimated 0.3 MeV/f in the region < 0.3 MeV. The spectrum is
obtained by fitting the histogram with a continuous curve in such
a way, that within each group the shape of the spectrum resembles
that of the corresponding part of the spectrum from the continuous
belt measurements, and the curve is normalized to 7.0 MeV/f.
3.
URANIUM CAPTURE GAMMA RAYS
238
The (n, Y)~ s P ec trum of U
has been investigated by
BARTHOLOMEW and HIGGS (1958). In the low energy region
SCHULTZ & al. (1957) have presented measurements on natural
uranium 9 but their paper gives the intensity only on a relative
Z38
scale, and is therefore difficult to relate to the U
spectrum of
BARTHOLOMEW and HIGGS. In Fig. 3 we have reproduced the
spectrum of BARTHOLOMEW and HIGGS, after normalizing it
239
to the last-neutron binding energy of U
f
4.70 MeV/capture .
(3.1)
235
The gamma ray spectrum from capture in U
has nots to
our knowledge, been measured. It has been conjectured by
BERTINI & al. (195 6) to use the same spectral distribution as for
prompt fission gamma rays. On the other hand GROSHEV & al.
(1958) have investigated the general shape of the unresolved part
of (n, v)-spectra for different compound nuclei of the same proton-
neutron parity. For even-even nuclei like U
, they show that
the continuous spectra start roughly at 1,5 MeV below the binding
energys increase to a maximum at about 2 or 3 MeV and then
decrease to zero. On this very approximate basisone can construct
O O c
a spectrum for U
OO £
1
(^ *'Y)
U
and normalize it to the bindning
energy
6.42 MeV/capture.
4.
7 ~\R
U
(3.2)
INELASTIC SCATTERING GAMMA RAYS
The differential inelastic scattering cross-sections
O T Q
cr(E t E , 9) of the energy levels E g. 1.75 MeV of U
have
o
been measured at 9 =90 for neutrons of energies E <. 2 MeV
by CRANBERG and LEVIN (1958). The integral inelastic scattering
cross-sections cr(E , E ) of the energy levels E
energies E
s
which for most
are equal to 4 7T<r(E , E , TT/2), have been calculated
by MANDEVILLE and KAVANAGH (1958), who have completed the
cross-section table of CRANBERG and LEVIN by some theoretically
deduced values.
Although the values of cr(E , E ) are given only for a few
neutron energies E , <r(E , E ) can be plotted for each E
as a
function of E »if the total inelastic scattering cross-section
<r (E ) = / <r (E , E )
v
n' l_j v y* n'
is known. Compilations of data on<r(E ) (CRANBERG and LEVIN,
HUGHES and SCHWARTZ 1958) cover the energy range E ^ 2 , 5
MeVj at 3.5 MeV it is possible to obtain a point at 3. 1 barns from
a comparison of the integrals of the spectra of inelastically
scattered 2.5 MeV and 3.5 MeV neutrons» as reported by FETISOV
(1957). It thus seems that the total cross-section
<r(E ) levels off
to about 3 barns at energies E > 2 MeV. The plots of <r(E , E )
and 2(E ) are shown in Fig. 4.
For E < 2 MeV the intensity of each gamma line (of energy
E ) is represented by the integral
1) In his recent compilation HOWERTON (1958) suggests about
2.5 barns. When this value is inserted in (4. 8), the figure
0. 8 MeV/f in table 2 changes to 0. 7 MeV/f.
eV
a M
jyiev
E
\ N(E )P [ r S ( E , E )] dE ,
n
V Oj n ' c L V Y n
(4.1)
where
v • N(E )) = uncollided fission neutron spectrum»
P
[ r S ( E ) E )] = probability that a neutron of energy E
23 8
collides with a U
- a t o m and excites t h e E - l e v e l , and
r = r a d i u s of the fuel e l e m e n t .
The intensity i s obtained in MeV/f j h o w e v e r , both S(E , E )
and r a r e dependent on the choice of r e a c t o r and fuel e l e m e n t s , and
the i n t e g r a t i o n will t h e r e f o r e b e left to the l a s t s e c t i o n .
The h a r d e s t gamma line of CRANBERG and LEVIN i s actually
not one line but a n u m b e r of lines a r i s i n g from s e v e r a l energy levels
between 1.4 and 1.75 MeV. At still higher e n e r g i e s the level density
i n c r e a s e s and the s t a t i s t i c a l theory should become a p p l i c a b l e . F r o m
the r e v i e w a r t i c l e of KINSEY (1957), a s s u m i n g a constant c r o s s s e c t i o n cr(E ) = a" in the s t a t i s t i c a l region^ the s p e c t r u m of i n e l a s t i c a l
ly s c a t t e r e d neutrons can be e x p r e s s e d a s
w(E n )
,Q
n
e/
F ( e , E n ) d e = const. ^ E +<^ < e e ~
de ,
(4.2)
where
Q = bindning energy of a neutron in the compound nucleus^
co(E ) = const. E ~ '
n
e
9
t h e level density a t the b o m b a r d -
ing energy E ,
n
E
d
G =-T=p—In w(E ) =
n
n
s the n u c l e a r t e m p e r a t u r e
aVE + 5 / 4
introduced by Weisskopf
and
238
a i s a constant^ which for U
— 1 /2
h a s t h e value 5.25 MeV
'<
If we n o r m a l i z e t h e s p e c t r u m (4. 2) by the r e q u i r e m e n t
E
r
n'
F ( e , E j de = E^ ,
(4.3)
we obtain the fraction F(e a E )dedE
of all bombarding neutrons
of energy
6 7 between E
n and En + dEn which are scattered into the
energy i n t e r v a l between e and e + de ,
FfcjEjdedE^
)de dE =
n
n
n
.2
j _ En \
n \
9
-_— .
/e
_-En'
(4.4)
n'
The total energy released as gamma radiation is then given by an
integral like (4. 1), where E - e is substituted for E , and where
P (r2) now is a constant, since ar was assumed constant in the
C
region of interest (E
> 2 MeV):
E
f
dE
2 MeV
n C"
n
0
Substitution of (4.4) in (4.5), and integration over the integral in
e gives
-E /9
(2+E n /9)-(2+3E n /9)e
v - Pc v—/
( r S )j\ N(E
- vx ~ n)•
# 9.
; v ' 21MeV
n'
-p E=
/
1 - ( 1 - -E^ -
n
^ / _e
\2 - E
\ J e- En TB
dE .
n
(4. 6)
'
x
In o u r c a s e E / 9 >5>i (with a m i n i m u m value = 8. 67 at 2 MeV) s o
n
that (4. 6) can be simplified to
oo
vP
(rS) \ N(E ) (29 + E )dE .
cx ' J v n' x
n'
n
2 MeV
(4.7)
The integral has the value 1.61 MeV per inelastically scattered
neutron. When v =2.47 neutrons/f, the expression (4.7) takes me
value
4.0 P (rS) MeV/f-
(4.8)
The spectral distribution of this radiation is unknown. If all the
excitation energy were radiated as ground-state transitions
the spectrum would be given by the integrand in (4.7). Since this
is not the case, the spectrum is considerably softer, with a peak
somewhere between 1 and 2 MeV. As a rough estimate we assume
that 3 P c (r£) MeV/f has the distribution of the integrand in (4.7),
and the remaining quarter is distributed in the region < 2 MeV in
such a way that the spectrum becomes zero at zero energy and is
continuous at 2 MeV.
5.
GAMMA RAYS FROM CAPTURE IN POISON» CONSTRUCTION
MATERIALS AND MODERATOR
After short irradiation times almost all the poison in the reactor
135
fuel is Xe
3 for which both the capture gamma spectrum and the
total energy release per capture (the binding energy of Xe
12
unknown. After a year ' s irradiation time in a flux of 1 0
n/cm s the Xe
) are
14
- 10
-fraction in the posion is still over 50 %, so that
it is not worthwhile to investigate the spectra of the other poison
components in any detail (BLOMEKE and TODD, 1957).
J o /
The binding energy of the two last neutrons in Xe
is 14. 5
MeV» which suggests that we adopt the figure
8 MeV/capture
(5.1)
as the approximate total energy release.
The capture gamma spectra of other absorbers present in the
construction materials, the coolant or the moderator can be found
in the recent compilations of GROSHEV & al. (1959)* BARTHOLOMEW
and HIGGS (1958) or DELOUME (1958).
6.
GAMMA RAYS FROM DISINTEGRATION OF CAPTURE
PRODUCTS
_
.
, ,
. __ 136
,
t
TT239 TT236
The main capture products are U
* U
and Xe
t of
239
which only U
is radioactive. In addition there might be radio-
active capture products in the construction materials, the coolant
239
239
and the moderator. U
disintegrates to Np
by emission of one
239
239
photon of 0. 074 MeV. Np
disintegrates in turn to Pu
in a
complicated way, by emission of soft (< 0.35 MeV) gamma rays.
From the decay schemes suggested by STROMINGER & al. (195 8 a, b)
and by DZEPELOV and PEKER (1957) one obtains a total energy
release of approximately 0.4 MeV per disintegration, including
239
the single line of U
.
At saturation (times large compared with the half-lives
239
239
of U
t 23.5 m and Np
, 2.33 d) every neutron capture in
238
2 39
U
is followed by one
disintegration of a U
nucleus and one
239
disintegration of a Np
nucleus, so that the net energy release
is
0.4 MeV/capture in U
238
(6.1)
The approximate spectrum is given in table 1 below.
Table 1.
Gamma energy release from disintegration of U
Energy range
MeV
0.05
0.10
0.15
0.20
0.25
0.30
7.
-
239
Energy release
MeV/capture
0,10
0.15
0.20
0.25
0.30
0.35
0.109
0.046
0
0.091
0.125
0.027
TOTAL GAMMA SPECTRA. APPLICATION TO THE
SWEDISH R3-REACTOR
The R3-reactor is a UO9 -fueled, D-, O-mode rated and D,OLt
Li
Lt
cooled reactor to be operated at 125 MW. The fuel elements contain
43. 5 % UO2 by volume, 46.4 % D£O at about 220° C and 10. 1 % Zr,
and they are arranged in the moderator on a square lattice with a
lattice pitch of 27 cm (MARGEN & al. 1958).
In natural uranium, there are
238
0.66 thermal captures in U
per fission» and
a=0.i9
"
"
" U
"
"
Tin
The number of neutrons captured in U
-resonances per
fission is given (see for instance WEINBERG and WIGNER, 1958,
p. 179) by
10
ve P f P r (i-p) ,
(7.1)
where
v = Z.47 fission neutrons produced per fission
8 = 1 . 03, the fast fission factor
p = 0.89» the resonance escape probability
P f = the fast non-leakage probability
P
= the resonance non-leakage probability
2
-4
-2
B a 2.4 • 10
cm 3 the buckling of the reactor core* and
T = 160 cm , the Fermi age.
With these values, the expression (7.1) becomes 0.27 captures/f.
238
239
The total number of capture reactions U
fission is thus 0.66 + 0.27 = 0.93 captures/f.
(n, v) U
per
This factor and the
figures in (3.1) and (6.1) give
238
4. 37 MeV/f released as U
capture gamma radiation, and
0.37 MeV/f
"
" U 2 3 9 decay
"
"
a times the figure in (3.2) gives
-p o r
1.22 MeV/f released as U
capture gamma radiation.
The number of neutrons absorbed in poison* construction
materials and moderator per fission is given by
v
1-f
n
f
<7'2>
-
where
— =s 1.85 neutrons absorbed in U per fission, and
f = 0.94, the thermal utilization factor.
With these values, the expression (7.2) becomes 0.12 captures/f.
In order to find the proportions of neutrons absorbed in Xe, Zr and
D?O respectively, we weight the components with the product of
neutron flux and macroscopic cross-section in the homogenized
lattice cells. The cross-section of Xe is given in terms of barns per
2 oc
original number of U
We find
atoms, by BLOMEKE and TODD (1957).
0.079 captures in Xe per fission
0.029
"
" Zr "
"
0.012
"
" D
"
"
Ii
Using the binding energies 8 MeV for Xe, 6.97 MeV for Zr and
6.24 MeV for D, the energy release becomes
Xe: 0. 63 MeV/f
Zr: 0.20
"
D,O: 0.07
it
238
The contribution from inelastic scattering in U
is found
by calculating the collision probability P (r2), which was introduced
C
in (4.1). P (r2) has been computed for uniform source strength
distributions and different source geometries by PLACZEK & al.
(1953). For a homogenized fuel element of radius 5. 62 cm the
total energy released in inelastic scattering is found to be 0.8
MeV/f.
In table 2 we collect all gamma sources together and compare
them with a previous calculation by BRAUN (1957) on a similar
J238
reactor. The largest difference is found to arise from the u
capture, where BRAUN has used a binding energy of 7.5 MeV
instead of 4.7 MeVj influenced by the value of the average binding
energy per nucleon (which is approximately 7.5 MeV for U
)
and by a gamma line at 7.5 MeV reported by KENNEY and
MATTINGLY (1956), but not found later (BARTHOLOMEW and
HIGGS, 1958).
Table 2.
Total gamma energy release.
Energy release (MeV/f)
Source
Present
BRAUN
Prompt fission
7.9
7.8
Fission products
TT238
U
capture
7.0
7.2
TT235
U
capture
Inelastic
scattering
1 3 5
v
Xe
capture
4.37
j
1.22
0.83>
0.27 1 )
U
0.37
Other decay
Total
1) Zr and D2O
0.9
0.63
Other capture
decay
8.2
22.6
2) Al
i.o 2 )
Ö.42)
25.5
3) Cf footnote on p. 5.
12
The resulting total spectrum is shown in Fig. 5. The spectrum of
radiation escaping from a fuel rod can be found by multiplying the
total spectrum by the energy-dependent escape probability P
for photons of energy E. P
(E)
(E) has been investigated by STORY
6SC
(1957) for a uniform source strength distribution and for a stepfunction approximation to the real source strength distribution in
cylindrical fuel rods.
However, it can be shown in the energy range covered by
STORY» that a simplified calculation taking into account only the
first absorbing collision and assuming a uniform source strength
distribution gives a result which lays well between the maximum
and minimum curves of STORY. The escape probability would thus
be given by
where
P
is the collision probability of PLACZEK, and \i
(E) is
the energy absorption coefficient for photons of energy E in the
homogenized rod of radius r.
The integral of the spectrum of escaping radiation, shown
in Fig. 5, is found to be 7. 6 MeV/f, which can be compared with
the figure 8. 6 MeV/f of BRAUN. The fraction of gamma energy
escaping from the fuel rod is thus approximately i / 3 .
In table 3 we give the integrals over 8 energy groups of the
spectrum of escaping radiation, S(E)» and the average energies
of these groups, defined as
E.
E. = \
E.
S(E) E d E / \
il
S(E) d E.
i
13
Table 3.
Energy groups of the spectrum of escaping radiation.
E
i
Energy interval
MeV
i
MeV
1
0 - 1
0.7
2
1 - 2
1.5
3
2-3
2.4
1.30
2.92
1.91
4
3-4
3.4
0.88
5
4-5
4.3
0.36
6
5.4
0.88
7
5 -6
6 -7
6.2
0.12
8
7-8
7.4
0.02
0-8
2.1
7.59
Total
Released energy
MeV/f
ACKNOWLEDGEMENTS
For valuable discussions and helpful suggestions the author
is indebted to Messrs. J . S . Story* Harwell, J. Braun and
N. G. Sjöstrand, AB Atomenergi.
REFERENCES
BARTHOLOMEW G. A. and HIGGS L.A. (1958) Compilation of
thermal neutron capture gamma rays. AECL-669.
BERTINI H.W., COPENHAVERC.M., PERRY A.M. and
STEVENSON R . B . (1956) ORNL-2113.
BLOMEKE J.O. and TODD M.F. (1957) Uranium-235 fissionproduct production as a function of thermal neutron flux, irradiation
time, and decay time. ORNL-2127, pt I-II.
BRAUN J. (1957) Gamma volume-sources in the reactor core.
AEF 88, AB Atomenergi-report in Swedish.
CRANBERG L. and LEVIN J . S . (1958) Inelastic neutron scattering
by U 2 3 8 . Phys. Rev. U>9, 6, 2063-2070.
DELOUME F . E . (1958) Gamma ray energy spectra from thermal
neutron capture. APEX 407.
DZEPELOV V.S. andPEKER L.K. (1957) Decay schemes of radioactive isotopes. AECL-457.
FETISOV N.I. (1957) Spectra of neutrons inelastically scattered on
U 2 3 8 . Atomn. Energ. 3, 9» 211.
GROSHEV L . V . , DEMIDOV A.M., LUTSENKO V.N. and
PELEKHOV V.I. (1958) Thermal-neutron capture gamma-ray
spectra and nuclear level distribution. Presented as P/2029 in
Geneva 1958.
GROSHEV L . V . , DEMIDOV A.M., LUTSENKO V.N. and
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The scattering
15
MARGEN P . H . , CARRUTHERS H . , HARGÖB., LINDBERG G.
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235
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~
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Trilinear chart of nuclides. Oak Ridge.
16
WEINBERG A.M. and WIGNER E . P . (1958) The physical theory of
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JETP, 32, 263-268.
~"
MeV
f.MtV
J._
i
4..
3..
\
\V
2 .
\
1 .
\
X
0
Fig. 1.
f
3
4
S
6
7
6 MeV
Spectrum of gamma rays emitted promptly (within i O
after fission. Normalized to 7.9 MeV/fission.
s)
'eV
r\
3
\
\
/
9
\
/
1
\
/
/
-^
0 /
HeV
Fig. 2.
Spectrum of gamma rays emitted by U
products, after 5»iO
thermal fission
s irradiation time and zero cooling time.
Normalized to 7.0 MeV/fission.
3
Fig. 3
AfeV
Z38
Z39
U
(n»v) U
gamma ray spectrurtij normalized to
4.70 MeV/capture.
2p
Fig. 4. Total inelastic scattering cross-sections cr
MeV
and inelastic
scattering cross-sections <r (E * E ) of gamma energy levels
MeV
MeV
f.MeV
11
å
10
I
9
A
8
7
//
f,
s
4-
j
J
\
3
\
\ \
\\
Z
v\
t
?
1
0
/
jj
•
0
MeV
Fig. 5. A. Spectrum of total gamma energy released in the R3 core
(scale on left).
B. Spectrum of gamma radiation escaped from the R3 fuel
elements (scale on right). The peaks at 4 MeV and 6.25 MeV
Z38
are due to capture in U
and Ds respectively.
Price Sw. cr. 4: —
Additional copies available at the library of
AB ATOMENERGI
Stockholm - Sweden
Affärstryck Offset 1959